The Dead Marshes were reeking wetlands that lay north-west of the Dagorlad and south-east of the Emyn Muil. The marshes were an endless network of pools and soft mires filled with water-courses, and in the dark waters could be seen the dead from battles of long ago.[1]

In T.A.1944 King Ondoher of Gondor was caught by a surprise attack by the Wainriders upon the Dagorlad. When the King and his guard were destroyed many of the confused soldiers of Gondor were driven by the attackers into the Dead Marshes.[4] However, after Eärnil II won the Battle of the Camp, those of the Wainriders who were not slain in the fight were themselves driven into the Dead Marshes and there perished.[5]

After Frodo and Sam had captured Gollum in the Emyn Muil (on 29 March 3019[6]), he revealed that he had found a hidden way across the Marshes.[8] The three took Gollum’s passage, where they saw candles and lights dancing about. Frodo was mesmerized by the lights and tried to reach out and touch the faces of the dead, at the bottom of the marshes. Gollum told them that the dead could not be touched, suggesting that he had once tried to eat them.[1]

In The Letters of J.R.R. Tolkien, Tolkien speculated that the description of the Dead Marshes may have been based on his personal experience in World War I, specifically, the Battle of the Somme.[9] When it rained, blast craters in no-man's land would become a series of pools or lakes with bodies of dead soldiers, from both sides, floating in them.